Our preliminary findings strongly suggest that muscle amino acids may be utilized as substrates by the T-cells of the immune system in HIV-infected individuals. The objective of this project is to determine the fate of muscle amino acids (esp. glutamine) in HIV-infected people before and after successful anti-viral therapy (protease inhibitors, etc.) The fate of the glutamine mitrogen will be followed in CD4 and CD8 lymphocytes, muscle and T-cell glutathione, and urine urea using stable isotopes tracer methodology and mass spectrometric detection.